Disubstituted aminouracils may be used to form xanthine and xanthine-related compounds. As illustrated below, one method for the synthesis of disubstituted aminouracils may include the process of condensation of a disubstituted urea (A) with cyanoacetic acid in acetic anhydride (1) followed by base-promoted cyclization (2).
Such a method produces a mixture of two isomeric disubstituted aminouracils (B) and (C). Thus purification may often be necessary to obtain a single isomer of the disubstituted aminouracil prior to additional processing to form a xanthine and/or xanthine-related compound. In fact, in some instances, obtaining a single isomer of the disubstituted aminouracil may not be feasible via condensation, since the condensation process may not be sufficiently selective and the ratio amounts of the two isomeric disubstituted aminouracils (B) and (C) may depend upon the relative size of the substituents and/or functional groups of the disubstituted urea (A).
It would be beneficial to provide a selective method for the synthesis of a variety of substituted aminouracils, and specifically disubstituted aminouracils, in order to selectively place functional groups at specific positions of the aminouracils prior to the formation of substituted xanthine and/or xanthine-related compounds.